COMPRESSED EARTH BLOCKS: MANUAL OF DESIGN AND CONSTRUCTION by Hubert Guillaud, Thierry Joffroy, Pascal Odul, CRATerre- EAG Volume II. Manual of design and construction A Publication of the Deutsches Zentrum fr Entwicklungstechnologien - GATE in: Deutsche Gesellschaft fr Technische Zusammenarbeit (GTZ) GmbH in coordination with BASIN - 1985

Scientific supervision: Patrice Doat, teaching architect; Hubert Guillaud, research engineer Authors: Hubert Guillaud, research architect; Pascal Odul, engineer architect; Thierry Joffroy, architect Illustrations: Oscar Salazar, architect; Patrick Idelman, draughtsman Documentation: Marie-France Ruault Format: Rgine Rivire English Translation: Claire Norton Publishing coordination: Titane Galer Photographs CRATerre-EAG: Dario Abgulo, Patrice Doat, Sbastien dOrnano, Hubert Guillaud, Hugo Houben, Thierry Joffroy, Serge Mani, Pascal Odul, Vincent Rigassi and additional assistance from: Sylvian Arnoux, Patrick Bolle, Anne-Sophie Clmenon, Christian Lignon, Christophe Magne, Philippe Romagnolo, Olivier Scherrer Drawings: CRATerre-EAG Cover photograph (Fig. 1): Rented house, Mayotte, Built by SIM. Die Deutsche Bibliothek - CIP-Einheitsaufnahme Compressed earth blocks: A publication of Deutsches Zentrum fr Entwicklungstechnologien - GATE, a division of the Deutsche Gessellshaft fr Technische Zusammenarbeit (GTZ) GmbH in coordination with the Building Advisory Service and Information Network - BASIN / (Engl. Transl.: Claire Norton). - Braunschweig: Vieweg. NE: Norton, Claire (bers.); Deutsches Zentrum fr Entwicklungstechnologien Vol. 2. Manual of design and construction / Hubert Guillaud (III.: Oscar Salazar; Patrick Idelman). - 1995 ISBN 3-528-02080-6 NE: Guillaud, Hubert With the help of Architectural Research staff of the Department of Architecture and Urbanism (Direction de lArchitecture et de lUrbanisme - DAU) du Ministre de lEquipment, du Logement et des Transports All rights reserved

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Deutsche Gesellschaft fr Technische Zusammenarbeit (GTZ) GmbH, Eschborn 1995 Published by Friedr. Vieweg & Sohn Verlagsgesellscahft mbH, Braunschweig Vieweg is a subsidiary company of the Bertelsmann Professional Information. Printed in Germany by Hoehl-Druck, Bad Hersfeld ISBN 3-528-02080-6

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Content

Acknowledgment................................................................................................... 5

Preface ................................................................................................................... 8

Introduction ......................................................................................................... 10 Historical background ................................................................................................... 10 Advantages of CEBS.................................................................................................... 11 Production .................................................................................................................... 12 The CEB as a building material .................................................................................... 14 Main characteristics...................................................................................................... 17 A building tradition ........................................................................................................ 18 The exposed wall's harmonious appearance ................................................................ 19 Architecture for housing................................................................................................ 19

1.Masonry principles........................................................................................... 22 Mortar ........................................................................................................................... 24 Bonding patterns .......................................................................................................... 27 Coursing ....................................................................................................................... 36

2.The project's building dispositions ................................................................ 41 Types of wall ................................................................................................................ 42 Types of structure......................................................................................................... 44 Foundations and footings ............................................................................................. 46 Openings...................................................................................................................... 57 Reinforcement .............................................................................................................. 62 Floors: structures.......................................................................................................... 65 Jack arches and vaulting .............................................................................................. 67 Roof classification......................................................................................................... 67 Finishings ..................................................................................................................... 74 Installing technical systems .......................................................................................... 78 Characteristic strength of CEBS................................................................................... 81 Permissible constraints................................................................................................. 85 Building economics....................................................................................................... 90

3.Architecture ...................................................................................................... 95 Architectural achievements or projects ......................................................................... 95 Architecture for housing................................................................................................ 95 Architecture for public buildings.................................................................................. 155

Bibliografy.......................................................................................................... 191

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Acknowledgment GATE - stands for German Appropriate Technology Exchange. It is a division of Deutsche Gesellschaft fr Technische Zusammenarbeit (GTZ) GmbH, an organization owned by the Government of the Federal Republic of Germany which commissions the GTZ to plan and implement Technical Cooperation activities with countries of the Third World. GATE was established in 1978 on behalf of the German Federal Ministry for Economic Cooperation (BMZ) - which is responsible for development cooperation with Third World countries - and in consultation with the German Federal Ministry for Research and Technology (BMFT). GATE currently works in the fields of dissemination of appropriate technologies, environmental protection and conservation of natural resources. Within the GTZ, GATE is responsible for these activities on a cross-sectoral basis. GATE, with the "Information Service on Appropriate Technology (ISAT)" works in the following areas: 1) Dissemination of appropriate technologies Dissemination and application of appropriate technologies, especially in connection with self-help activities - Cooperation with non-governmental appropriate technology groups: cooperation with NGO's in

Africa, Asia, Oceania and Latin America. - Information service: documentation (appropriate technologies), exchange of information,

question and answer service, publication of technical brochures, articles and a technical journal. - Fund for small-scale appropriate technology projects. 2) Environmental protection and conservation of natural resources - Coordination of environmental protection activities at the GTZ. - Further development of methods and instruments for environmental impact assessment. - Technical backstopping and coordination of interdisciplinary and multisectoral projects in the

fields of environmental protection and conservation of natural resources. - Cooperation with the relevant national and international organizations, associations and offices

concerned with this sector. German Appropriate Technology Exchange - GATE in: Deutsche Gesellschaft fur Technische Zusammenarbeit (GTZ) GmbH Posffach 5180 / D-65726 Eschborn / Germany / Phone: (06196) 79-0 / Telex: 407 501 0 gtz d / Fax (06196) 79 48 20 CRATerre-EAG - The International Centre for Earth Construction - School of Architecture of Grenoble. The members of CRATerreEAG are high-level professionals from various countries. Since 1973, CRATerre-EAG has been involved full time in all aspects of earthen architecture from the preservation of historic monuments to the setting up of modern production lines. CRATerre-EAG's five inter-related fields of activity are: 1) Research: as an officially recognized research team, CRATerre-EAG carries out several research programs at fundamental and practical levels in various fields such as ethnology, economy, mineralogy, soil mechanics, technology, etc. 2) Consultancy: CRATerre-EAG's missions in this field cover the project formulation, feasibility and

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investment studies, setting up of programs, building design, raw material prospection, planning and evaluation. 3) Application: CRATerre-EAG members are currently engaged in field operations from architectural design to site supervision of social or educational building on behalf of governmental or non-governmental organizations. 4) Training: in collaboration with the School of Architecture of Grenoble (EAG) and Grenoble University (USTMG), CRATerre-EAG runs post-graduate courses for architects and building engineers. CRATerre-EAG also organizes vocational training courses and thematic intensive training sessions in collaboration with organizations such as the International Union of Testing and Research Laboratories for Materials and Structures (RILEM), International Council for Building Research Studies and Documentation (ClB), United Nations Industrial Development Organization (UNIDO), International Centre for the Study of the Preservation and Restoration of Cultural Property (ICCROM) and others. 5) Dissemination: through the publication of scientific and technical books and manuals, an active participation in international meetings and a "question-and-answer" service, CRATerre-EAG contributes greatly to the promotion of earthen architecture and the dissemination of technical information. CRATerre-EAG Maison Levrat / Parc Fallavier / BP 53 / F - 38092 Villefontaine Cedex / France / Telex: 308 658 F / Fax: (33) 74 95 64 21 Scientific supervision: Patrice Doat, teaching architect; Hubert Guillaud, research architect; Hugo Houben, research engineer Authors: Hubert Guillaud, research architekt; Pascal Odul, engineer architect; Thierry Joffroy, architect Additional assistance: Vincent Rigassi, architect; Alexandra Douline, senior technician; Philippe Gamier, architect Illustrations: Oscar Salazar, architect; Patrick Idelman, draughtsman Documentation: Marie-France Ruault Format: Rgine Rivire English Translation: Claire Norton Publishing coordination: Titane Galer Photographs CRATerre-EAG: Dario Angulo, Patrice Doat, Sbastien d'Ornano, Alexandre Douline, Hubert Guillaud, Hugo Houben Thierry Joffroy, Serge Mani, Pascal Odul, Vincent Rigassi and additional assistance from: Sylvain Arnoux, Patrick Bolle, Anne-Sophie Clemencon, Christian Lignon, Christophe Magne, Philippe Romagnolo, Olivier Scherrer Drawings: CRATerre-EAG Cover photograph (Fig. 1): Rented house, Mayotte. Built by SIM. Die Deutsche Bibliothek- ClP-Einheitsaufnahme Compressed earth blocks: A publication of Deutsches Zentrum fur Entwicklungstechnologien - GATE, a division of the Deutsche Gesellschaft fur Technische Zusammenarbeit (GTZ) GmbH in coordination with the Building Advisory Service and Information Network - BASIN / (Engl. transl.: Claire Norton). - Braunschweig: Vieweg. NE: Norton, Claire (Ubers.); Deutsches Zentrum fr Entwicklungstechnologien < Eschborn >

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Vol. 2. Manual of design and construction / Hubert Guillaud... (111.: Oscar Salazar; Patrick Idelman). - 1995 ISBN 3-528-02080-6 NE: Guillaud, Hubert With the help of Architectural Research staff of the Department of Architecture and Urbanism (Direction de l'Architecture et de l'Urbanisme - DAU) du Ministre de l'Equipement, du Logement et des Transports All rights reserved Deutsche Gesellschaft fr Technische Zusammenarbeit (GTZ) GmbH, Eschborn 1995 Published by Friedr. Vieweg & Sohn Verlagsgesellschaft mbH, Braunschweig Vieweg is a subsidiary company of the Bertelsmann Professional Information. Printed in Germany by Hoehl-Druck, Bad Hersfeld ISBN 3-528-02080-6 This book is the fruit of patient and methodical team-work carried out in the course of fifteen years of scientific and technical research, within the CRATerre research laboratory of the School of Architecture of Grenoble, on compressed earth block technology and its architectural applications, closely linked to experimentation and to site-work, as well as to university teaching and professional training. Designed with the intention of widely disseminating theoretical knowledge as well as practical skills, a large part of the book is devoted to practical examples of construction techniques and architectural design, which are the central themes. It is important to provide a wider public of land-use decision-makers, architects and engineers, entrepreneurs and builders, with the information and tools needed to ensure a high quality of architectural application, which alone can ensure the social, cultural and political acceptance of this technology. With its attractive layout and the answers it provides to all the practical questions that site practitioners might ask, this book seeks to impart confidence in a construction technology, which is still historically young and not sufficiently known. It emphasizes the link between building material, structure, form, and architectural detailing. But it also addresses the importance of the technology with regard to economic and social benefits for the local population, as are confirmed by some of the project examples presented in it. "A building material is interesting not for what it is, but for what it can do for society." John Tumer's aphorism remains remarkably relevant today, and, in many situations, the compressed earth block has already proved its ability to play a significant role in providing affordable and decent shelter for all levels of society. The reader of this will be a committed practitioner with a better understanding of the technology of compressed earth blocks and ready to play a useful role in society.

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Preface Compressed earth block technology, which is anchored in an initial concern to provide a new, economically and socially relevant response to housing production for the very poor, has continued to focus on this concern as its area of application has developed. Tens of thousands of family or communal homes and educational and health facilities have indeed been built since the early 1950s, when this building material emerged in its present form, at the CINVA Centre in Bogota, Colombia. These buildings have gradually confirmed the appropriation of this building technology. This simple building material, directly descended from the most ancient building traditions of the unbaked earth brick and from the fired brick, is capable of the same building and architectural subtlety and the same capacity for adaptation to the broad spectrum of factors - physical, ecological, social, economic and technical -which dictate the production of the built environment. As a building material, it has come to the fore by demonstrating its usefulness, which can be measured in technical and economic, but also in human terms. From a technical point of view, compressed earth block technology is firmly propped up by a scientific body of knowledge which is the equal of knowledge developed for other kindred building materials used in masonry. From an economic point of view, the compressed earth block, which has the advantage of being able to be locally produced and directly used, is today comparable and sometimes more competitive, depending on the context in which it is applied. As far as production and construction distribution chains are concerned, the technology generates employment across a wide range of jobs, from quarrying to brick-manufacturing, from builder to entrepreneur. In architectural terms, the compressed earth block ensures high quality results and at the same time, given optimum conditions of use, enables the foreign currency and energy savings which are essential to its relevance from a development point of view. At a human level, this technology provides concrete responses to the basic issue of improving the built environment and therefore the well-being of societies. Better quality construction and architecture, accessibility and replicability are the main criteria for evaluating this relevance from a human and economic view-point. But this relevance is possible only if the scientific and technical body of knowledge has been mastered, as well as the practical skills. This book supplies the intellectual and practical tools required for a correct application of compressed earth block technology in the field. This book is also the fruit of patient and methodical team work, with the underlying objective of achieving the scientific, technical, social and cultural ratification of a new technology, the useful potential of which was obvious from the very first. Our intuition of this usefulness still, however, had to be confirmed. But today, we are talking about a technology which has not only achieved a level of industrial potential with production methods suited to the formal production sector, but also been able to remain on the scale of craft production and safeguard a degree of usefulness which is relevant to informal sector applications. This dual advantage can serve a wide range of architectural applications in the field of both housing and public facilities. The success of contemporary cases, notably the example of applications on the island of Mayotte (Comoro), confirms this dual advantage placed at the service of development ensuring economic and social spin-offs for the local population. This ratification needed to be confirmed by building up a body of knowledge and skill capable of being transmitted and appropriated, starting from high quality architectural examples. This is in fact what has in many instances occured, as is shown in the monographs which form the second part of this book, a book intended as much for land-use decision-makers as for architects, engineers or entrepreneurs; a book designed to boost confidence and supply the practical tools which seem to us, at the term of our research and field experience, indispensable; a book designed to disseminate this knowledge and skill towards a wider area of application, but most particularly towards housing and public facilities for local communities who have no choice but to use earth as a basic building material and who have a legitimate desire to benefit from modern technology. Such is compressed earth block technology, at the crossroads between traditional earth building customs and modern masonry building practices, a technology which offers an alternative whilst remaining within a range of high quality architectural applications. This book has been made possible thanks to the active collaboration which has developed over

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recent years between our team and the international non-government organisation MISEREOR and with GATE/GTZ (German cooperation) in the field of dissemination of appropriate building technologies, through training and pilot architectural applications. Our particular/hanks are due to Mr. Herbert Mathissen and Mrs. Hannah Schreckenbach, from these two organisations respectively, for the help they have given us with the preparation of the book as well as for the trust which they have placed in their authors in order for the project to succeed. We also wish to thank all those involved in the field - architects, entrepreneurs, builders and brick-makers - who have enabled the implementations of compressed earth block architecture, which are given as examples in this book, to occur and thus strengthened the potential, in terms of usefulness and quality, of this technology. May their example be followed by yet more practitioners following on in the same spirit as their predecessors, whose intention today is to share their knowledge and experience. Hubert Guillaud, Hugo Houben, CRATerre-EAG researchers.

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Introduction

Historical background The compressed earth block is the modern descendent of the moulded earth block, more commonly known as the adobe block. The idea of compacting earth to improve the quality and performance of moulded earth blocks is, however, far from new, and it was with wooden tamps that the first compressed earth blocks were produced. This process is still used in some parts of the world. The first machines for compressing earth probably date from the 1 8th century. In France, Francois Cointeraux, inventor and fervent advocate of "new pise" (rammed earth) designed the "crecise", a device derived from a wine-press. But it was not until the beginning of the 20th century that the first mechanical presses, using heavy lids forced down into moulds, were designed. Some examples of this kind of press were even motor-driven. The fired brick industry went on to use static compression presses in which the earth is compressed between two converging plates. But the turning point in the use of presses and in the way in which compressed earth blocks were used for building and architectural purposes came only with effect from 1952, following the invention of the famous little CINVA-RAM press, designed by engineer Raul Ramirez at the ClNVA centre in Bogota, Columbia. This was to be used throughout the world. With the '70s and'80s there appeared a new generation of manual, mechanical and motor-driven presses, leading to the emergence today of a genuine market for the production and application of the compressed earth block.

A highly developed technology Since its emergence in the '50s, compressed earth block (CEB) production technology and its application in building has continued to progress and to prove its scientific as well as its technical worth. Research centres, industrialists, entrepreneurs and builders have developed a very sophisticated body of knowledge, making this technology the equal today of competing construction technologies. CEB production meets scientific requirements for product quality control, from identification, selection and extraction of the earth used, to quality assessment of the finished block, thanks to procedures and tests on the materials which are now standardised. This scientific body of knowledge ensures the quality of the material. Simultaneously, the accumulated experience of builders working on a very large number of sites has also enabled architectural design principles and working practices to emerge and today these form practical points of reference for architects and entrepreneurs, as well as for contractors.

Role in development The setting up of compressed earth block production units, whether on a small-scale or at industrial level, in rural or urban contexts, is linked to the creation of employment generating activities at each production stage, from earth extraction in quarries to building work itself. The use of the material for social housing programmes, for educational, cultural or medical facilities, and for administrative buildings, helps to develop societies' economies and well-being. CEB production forms part of development strategies for the public and the private sector which underline the need for training and new enterprise and thus contributes to economic and social development. This was the case in the context of a programme on the island of Mayotte, in the Comoro islands, for the construction of housing and public buildings, a programme today regarded as an international reference. The use of CEBs which followed the setting up of an island production industry proved to be pivotal in Mayotte's development, founded on a building economy generating employment and local added value in monetary, economic and social terms.

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Social acceptance CEB represents a considerable improvement over traditional earth building techniques. When guaranteed by quality control, CEB products can very easily bear comparison with other materials such as the sand-cement block or the fired brick. Hence the allegiance it inspires amongst decision-makers, builders and end-users alike.

The future of CEBs CEB technology has made great progress thanks to scientific research, to experimentation, and to architectural achievements which form the basis of a wide range of technical documents and academic and professional courses. A major effort is now being devoted to the question of norms and this should help to confer ultimate legitimacy upon the technique in the coming years.

Advantages of CEBS The CEB technique has several advantages which deserve mention: - The production of the material, using mechanical presses varying in design and operation,

marks a real improvement over traditional methods of producing earth blocks, whether adobe or hand-compacted, particularly in the consistency of quality of the products obtained. This quality furthers the social acceptance of a renewal of building with earth.

- Compressed earth block production is generally linked to the setting up of quality control

procedures which can meet requirements for building products standards, or even norms, notably for use in urban contexts.

- In contexts where the building tradition already relies heavily on the use of small masonry

elements (fired bricks, stone' sand-cement blocks), the compressed earth block is very easily assimilated and forms an additional technological resource serving the socio-economic development of the building sector.

- Policy-makers, investors and entrepreneurs find the flexibility of mode of production of the

compressed earth block, whether in the rural or the urban context, small-scale or industrial, a convincing argument.

- Architects and the inhabitants of buildings erected in this material are drawn to the architectural

quality of well-designed and well-executed compressed earth block buildings.

Technical performance Compacting the soil using a press improves the quality of the material. Builders appreciate the regular shape and sharp edges of the compressed earth block. The higher density obtained thanks to compaction significantly increases the compressive strength of the blocks, as well as their resistance to erosion and to damage from water.

Flexibility of use The wide range of presses and production units available on the current market makes the material very flexible to use. With production ranging from small-scale to medium and large-scale semi-industrial or industrial, CEBs can be used in rural and urban contexts and can meet very widely differing needs, means and objectives.

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Standards and models Compressed earth blocks are of standard sizes and meet quality requirements which are suitable for carrying out large housing or infrastructure programmes, based on the design of architectural models. These standard block sizes and shapes, as well as the architectural models, can be defined before the programme begins, at the design stage, with great flexibility.

Highly practical nature of the technology The common dimensions of CEBs lend themselves to great flexibility of use in various building solutions, as load-bearing masonry or as in-fill. CEBs can also be used for arches, vaults and domes, as well as for jack-arch floors.

Genuine architectural merit Very fine masonry work, equal to fired brick building traditions, can be realised thanks to the high quality of compressed earth blocks. The architectural application of CEBs can range from social housing to luxury homes and prestigious public buildings. Since the '50s, the experience of architects and builders has been considerably enriched by widely differing architectural realisations in all areas of application. Experimentation has to a large extent given way to technological and architectural expertise and has enabled CEB technology to evolve to the point where today it can be considered the equal of other construction technologies using small masonry elements.

An alternative to importation Whilst meeting the same requirements as other present-day building materials, the CEB also presents a technological alternative to imported materials, the use of which is often justified because of the need for standardisation. CEBs have the advantage of being produced locally, whilst still meeting this need.

Some constraints The quality of CEBs depends on good soil selection and preparation and on the correct choice of production material. Architectural use of the material must take account of specific design and application guidelines which must be applied by both architects and builders. This means that professional skills must be ensured by suitable training. From an economical point of view, CEBs can sometimes fail to be competitive with other local materials. A technical-economic survey will enable the feasibility of the technology to be determined in each application context.

Production The production of compressed earth blocks can be regarded as similar to that of fired earth blocks produced by compaction, except that there is no firing stage. Production will be differently organized, depending on whether it takes place in the context of small, "craft industry" units (or brickworks), or in the context of a semi-industrial or industrial unit. Production, drying and stocking areas will also vary depending on the methods of production selected and the production conditions dictated by the climatic, social, technical and economic environment.

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No production period or season is particularly favourable or unfavourable, providing that measures are taken in wet or hot seasons (if any) to protect production areas or storage areas. Generally speaking, as far as production rates are concerned, these will depend largely on the way production is organised and on the type of equipment used as well as on the skill of the labour-force. CATEGORIES OF PRESSES

Manual presses These are manually operated and carry out only the compression and ejection of the block. Light, mechanical and hydraulic presses fall into this category. Production outputs for these presses are in the order of 300 blocks per day. Mechanized manual presses also exist, and are generally heavier and more robust, but their outputs remain hardly any higher than that of light presses (up to 500 blocks per day).

Motorized presses These are motor-driven and carry out only the compression and ejection of the block. Mechanical and hydraulic presses fall into this category. Motorized mechanical presses form a new generation of presses, sometimes derived from heavy mechanized manual presses. They enable better rates of production and outputs can exceed 800 blocks per day. Hydraulic motorized presses, which are descended from pumping and oil-circuit mechanisms, should only be used in a favourable technological environment. Their viability should be checked.

Mobile production units (light) These are easily transportable, motorized and sometimes automated. In addition to the compression and ejection of the block, they also carry out raw material preparation operations and/or the removal of the products.

Fixed production units These are difficult to transport, motorized and sometimes automated. In addition to the compression and ejection of the block, they also carry out raw material preparation operations and/or the removal of the products. CLASSIFICATION AND CHARACTERISTICS The types of presses and production units which exist as a whole on the international market today can be classified (see Fig. 4) according to these four main categories and as a function of the systems they use (power source, energy transmission, compressive action) and their main characteristics (compressive force, theoretical output). As far as production output is concerned it should be stressed that the figures supplied by manufacturers fairly often refer to a press's theoretical mechanical cycle, but that on site stated outputs can be lower, as production is very closely linked to the way in which production is located and organized.

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SYSTEMS USED PRESS CATEGORIE

S

CHARACTERISTICS

POWER SOURCE

ENERGY TRANSMISSION

COMPRESSIVE

ACTION

COMPRESSION

PRESSURE

THEORETICAL SOURCE

OUTPUT /8 H mechanical static very low 300 to 800 manual mechanical and

hydraulic static manual

presses hyper 300 to 400

mechanical static low 400 to 1 000 mechanical static motorized

presses low to medium 800 to 3 000

hydraulic static low to medium 800 to 2 000 mechanical static low to medium 800 to 3 000 hydraulic static mobile

production units

low to medium 800 to 3 000

mechanical static low 2 000 to 15 000 motorized hydraulic and

mechanical static or dynamic

low to hyper 1 500 to 7 500

hydraulic static low to mega 3 000 to 50 000 hydraulic and

mechanical dynamic fixed

production units

1000 000 to 50 000

Fig. 4: Classification of presses for the production of compressed earth blocks (29.5 x 14 x 9 cm).

The CEB as a building material Compressed earth blocks are small masonry elements, parallelepiped in shape, but the common dimensions of which differ from those of hand-moulded earth blocks or of fired bricks and vary depending on the type of specially developed presses or moulds used. Two main criteria must, however, be taken into account when determining a compressed earth block's dimensions, which should above all be suited to the great degree of flexibility in use which is one of the great qualities of this building material. These are: - on the one hand the weight of the block, bearing in mind that they are solid blocks which are

principally used in masonry, - on the other hand the work (or nominal) dimensions of length (1), width (w) and height (h) which

will determine bonding patterns. For this reason, as a rule, compressed earth block production has mainly used dimensions consistent with a unit weight in the order of 6 to 8 kg and with the possibility of building walls 15, 30 or 45 cm thick. The most common nominal dimensions in use today are 29.5 x 14 x 9 cm (I x w x h), which gives a material which is very easy to handle and very flexible in the way it can be used for many configurations of wall and roof building systems jack-arch flooring, vaults and domes) and of arched openings.

There are 4 main families of blocks:

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1. Solid blocks These are mainly prismatic in shape. They fulfil very widely differing functions.

FIG. 1

2. Hollow blocks Generally the voids of hollow blocks account for a total of 5 to 10%, and up to 30% using sophisticated techniques. Voids can improve the adherence of the mortar and reduce the weight of the block. Certain hollow blocks can be used to build ring-beams (lost formwork).

FIG. 2

3. Perforated blocks These are light but require fairly sophisticated moulds and greater compressive force. They are suitable for reinforced masonry (in earthquake areas).

FIG. 3

4. Interlocking blocks These can be assembled without mortar, but they require sophisticated moulds and high compressive force. They are often used for non-loadbearing structures.

FIG. 4

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FIG. 5

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Main characteristics Comparisons between the characteristics and performances of the compressed earth block and those of other classic masonry materials, should not be restricted solely to taking account of their compressive strength or differences in production costs. The issue is a more complex one and any comparison should rather be based on a wide register of parameters, including: the shape and dimensions of the material, its appearance (surface, texture, attractiveness,) as well as a full range of measures of performance, such as - indeed - dry and wet compressive strength, but also thermal insulation, apparent density, and durability. But over and above this, aspects linked to the production and use of the material highlight all the complexity of such comparisons by taking account of such factors as the nature of the soil deposits supplying the raw material, the means by which this raw material is processed into a building material, the energy involved in this processing, the nature of the material when considered as a building component or element, and its state in the finished building, taking account of questions of durability and maintenance. This intelligent, way of comparing materials with each other, over and above scientific considerations intended to compare materials in laboratory conditions, takes account of the architectural and practical application of materials in situ. ASPECTS OF UTILISATION The position of the compressed earth block relative to other masonry materials can be established according to aspects of use of the material. Technical aspects Its mechanical, static, hydrous, physical etc. characteristics. Economic aspects Unit production cost, capital investment, etc. Health and safety aspects The emission of dangerous fumes, radioactivity etc. Psychological aspects The nature of the material, surface texture, colour, shape, luminosity, etc. Ecological aspects Deforestation, the hollowing out of hillsides as a result of quarrying, use of water and energy sources, production of pollution and waste material etc. Social aspects Economic and social spin-offs resulting from job creation, socio-cultural acceptability, etc. Institutional aspects Legislation, insurance, norms, development policies linked to the setting up of productive industries, etc. Taking these various aspects into account leads directly back to the need to carry out a preliminary technico-economic feasibility study before setting up a production system, for these considerations weigh heavily in the choice of system. The table (Fig. 7) shows simple points of comparison, but these should not overshadow the importance of these various aspects of utilization of the material.

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FIG. 6

A building tradition The very distant origins of the contemporary compressed earth block technique must be traced back to thousand year-old traditions of brick-making, first hand-shaped and then moulded. Building with the "thob" or "otoub" in Egypt as early as pre-dynastic epoches (3rd century B.C.), or in Mesopotamia, on the bountiful banks of the Tigris and the Euphrates, or again in the Indus valley, laid the foundations of "adobe" construction which is still to be found in these regions and which has radiated out to many countries. The use of the moulded earth brick remains linked to the fantastic evolution of mankind which took place between the agricultural revolution of the neolithic age and the urban revolution and corresponds to an advanced stage in the evolution of societies, and in the organisation of materials production and the building of dwellings. With the building of cities, the use of the earth brick was to be very quickly associated with architectural prowess. Building using small masonry elements indeed liberated man from the most rudimentary building technologies, such as waffle-and-daub or cob, which had restricted building and architectural performance. The advent of the earth brick enabled the most prestigious palaces, sanctuaries and religious temples of the great river civilizations (of the Nile, the Tigris and Euphrates, the Indus and the Huanghe) to be erected, multiplying the number of towns on fertile banks favourable to the installation of human settlements. Modern and contemporary archeological studies bear witness to the architectural genius of the builder of ancient times. The progression from the moulded earth brick technique to the compacted earth block corresponds to a logical improvement in the material. The increased density and reduced porosity resulting from compression improve the behaviour of the earth block in the face of the harmful effects of water. This compression technique was first practised manually using a tamp and always inside moulds' a painstaking technique giving poor quality blocks from the point of view of both appearance and

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mechanical performance. It was therefore logical that the technique should gradually evolve towards the development of machinery. The first presses emerged recently and were derived from the ceramic and calcium-silicate industries; there then appeared a new generation of presses specific to compressed earth block technology. This evolution from adobe, to compacted block and then to compressed earth block remains a logical progression in many regions, although very often the technological leap occurs directly between the adobe and the compressed earth block.

The exposed wall's harmonious appearance With the "modern movement" of the '20s end '30s, and then the "international style" of the '70s end '80s, came an architectural language which used precise shapes, sharp edges, and white facades made from industrialized building materials which demanded precise and regular assembly. This form of architectural language clearly revealed the predominance of the industrial machine over craftsmanship. With concrete, the modern material par excellence, anything was possible, both good and bad, but its use did not necessarily demand very high skills. In many cases, it must be admitted, the use of concrete is not linked to very sophisticated skills. Some very attractive architectural uses of concrete cannot disguise the overall mediocrity of contemporary architectural structures. At the same time, this modern and international architectural style has never really eclipsed the tradition of building using small exposed masonry elements which has remained common throughout the industrialized countries of Latin or Anglo-saxon origin. This latter architectural style is still perfectly contemporary and many architects are today once again giving pride of place to the brick in their work. Those who come across the compressed earth block generally find that it presents the same interest and flexibility in use, and that it links back to a traditional architectural language. Certain so-called "brick" countries (Great Britain, Belgium, Holland, etc.) have greatly developed the art of the large exposed masonry wall. Very great architects have used brick for their most beautiful works, both for housing and public buildings. The architectural language of the brick, with its multitude of formal variations in expression, has always been considered to be one of unparalleled flexibility and richness. In an inaugural speech in 1938 in Chicago, Mies Van der Rohe declared: Take a brick, how practical its small' convenient size, so handy for any use. What logic in its bonding and in the resulting texture. What richness in the most simple surface of a wall, and yet what a discipline this material imposes. Who better than Louis Khan has given expression to the seductiveness, the delight and harmony to be found in the contemporary architectural style of exposed bricks in which he finds a search for "romanity" and continuity? How impossible to dissociate the harmony of the exposed wall from the delight and pleasure of observing it. Present day compressed earth block architecture follows on in the succession of brick architecture and is its direct descendant. It plays its part in the continuity of the harmony of the exposed wall and the skills which unite architect and contractor. It is the link woven with history.

Architecture for housing Since the 1950s, which marked the emergence of the contemporary technology of compressed earth block construction, the scope of activity in terms of architectural realisations has continued to grow, both in industrialized and in developing countries. The compressed earth block provides a complete response to demands for modernity linked to the improvement of well-being and lifestyle in a comfortable, agreeable, and aesthetic built environment, which is in harmony with the environment. It also meets economic concerns, by enabling the most favourable socio-economic conditions of production, and, notably in countries which are dependent on an outward-looking construction economy based on the importation of materials, gives access to high quality housing at competitive costs. When the technique has been fully mastered in the context of a production industry which creates employment opportunities and skills, it gives rise to a "stock" of high quality architecture which can then become a reference programme. Such is the case with the compressed

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earth block architecture of the social housing and public facilities programme which was implemented in the Comoro islands, on the island of Mayotte. In France, the "romaine de la Terre" ("Earth Domain") project, which was completed in 1985 near Lyon, was a flagship operation for the renewal of earth architecture. The demonstrative value of this operation, from a technological and architectural point of view, opened the way for a renewal of earth architecture. IN FRANCE, THE "DOMAINE DE LA TERRE" The "romaine de la Terre" project was the physical embodiment of the idea, which had been advanced towards the end of the '70s, of once again using unbaked earth in the organized building sector. By succeeding in mobilizing all the normal actors involved in building production (planners and contractors, architects and entrepreneurs, technical standards offices and insurance companies, research centres, production equipment and building materials manufacturers), the project led the way for a new approach to building with earth, based on actual implementation. It also resolved a number of problems to which solutions had up till then not been found. Located in the Rhone-Alpes region, itself rich in rammed earth architecture, it forms a link between vernacular traditions and modernity. The "romaine de la Terre" operation, which provided local authority accommodation at modest rents, consists of 65 housing units, grouped into 12 lots of 5 to 10 semi-detached or terraced units. The earth block was one of the earth building techniques most used, with more then half of the buildings being built in vibration compacted Barth blocks, the remainder being built from rammed earth (compacted between shuttering) or taking the form of straw-clay (covering a wooden framework). The architectural quality of the built estate and the demonstration of the economic feasibility of this project, despite its experimental character, subsequently stimulated, both in France and abroad, through the value as an exemplary operation, a significant development in the realization of earth housing in general and using compressed earth blocks in particular. Compressed earth block architecture for housing progressed significantly during the 1980s, both in European and in developing countries. Progress in scientific, technical and architectural research on mastering the means of production of the material as well as its application, the implementation of numerous pilot or experimental programmes, and the dissemination of technical data amongst field operators, all contributed to the expansion of a building market specific to this material. The building industry was right, if one is to judge by the regular appearance on the market of new presses and other production equipment (mixers, grinders, etc.). Simultaneously, the increasing importance attached to training, at academic and at professional levels, and the development of sites linking production, construction and training, have helped to set up a network of skills favourable to the blossoming of a genuine body of knowledge. Finally, mention must be made of the support given by large international organizations, and notably the role played by UNIDO (United Nations Industrial Development Organization), and CID (Centre for Industrial Development) or UNCHS-Habitat (United Nations Centre for Human Settlements), linked to a cooperation effort on the part of European countries (France, Germany) in the promotion of this material and the support given to the setting up of compressed earth block production industries, notably in African countries. The example of the social housing programme in Mayotte (Comoro) remains most impressive: 6,000 low-cost houses and nearly 1,000 public buildings (primary and secondary schools, state offices) have been built in the space of 10 years on an island which in 1978 was still using wattle-and-daub and raffia. LOW-COST AND RENTED HOUSING

Marrakesh, Morocco There has been renewed interest in building with compressed earth blocks since the 1980s. Between the traditional rammed earth and abobe of the "ksour" of southern Morocco and the modern use of compressed earth blocks rendered with "taddelakt" (a coloured and smoothed lime render), the architect Elie Mouyal is a fervent promoter of this technique which he has exploited to build luxury homes framed by the greenery of palm groves (figs. 16 and 18).

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Mayotte, a Comores island The compressed earth block industry was developed on Mayotte from 1980-81 onwards, atthe initiative of the state public facilities department (Direction de l'Equipement) and the Mayotte Housing Company (SIM). The SIM design team and the architects settled on the island, desirous to make full use of local materials, very quickly become interested in this material, the technical qualities and architectural potential of which were to be very soon demonstrated in the first housing and public facilities buildings. These first projects were to pave the wayfor Mayotte's own architectural language, which was rapidly placed at the service of a new-born genuine housing stock. The use of compressed earth blocks was linked with other local materials (wood, raffia, basalt and phonolitic stone) as a real building skill developed founded on a knowledge of the characteristics and potentialities of these. Historic lever of development of a local architecture, the compressed earth block has become a local material introducing new skills to Mayotte's small contractors and craftsmen (figs. 19, 20 and 21).

Architecture for public buildings Promoting the compressed earth block, from the perspective of setting up a local production and construction industry, is an indispensable stage. Notably to overcome psychological barriers, as the compressed earth block remains a construction material which is linked in the minds not only of the people but also of professionals to the rustic nature of traditional materials, as opposed to sand-cement blocks. In this initial phase, the construction of public facilities buildings, as experience in a number of areas has shown, is a major asset with great political and social impact. On Mayotte, officials and locally-elected representatives, together with building professionals, from the outset realized the importance of the demonstrative value of built examples. The first pilot housing programmes were immediately linked to the construction of primary schools in the vicinity of the largest built-up areas of the island and in rural areas. Over an interval of ten years, all the administrative offices previously located together at "Petite Terre", Pamandzi, were to be transferred to Mamoudzou, the administrative capital of the island at "Grande Terre". The "Prefecture" (or main administrative building), and the offices of the departments of health and social affairs, of public facilities, and of education are of remarkable architectural quality and elegance and display their architects' intention to highlight the value of using the compressed earth block combined with other local materials and with the skills acquired by the island's craftsmen and contractors. ADMINISTRATIVE BUILDINGS, SCHOOLS, HOTELS

Burkina Faso and Morocco Many countries have adopted the approach of promoting the compressed earth block through the construction of public facilities in the context of implementing local materials construction strategies. In Burkina Faso and in Morocco, the compressed earth block has been used for building schools, university accommodation, or luxury tourist hotels which provide an opportunity to demonstrate/he quality of the material and the part it can play in high quality architecture. Such projects are the spear-head of a new confidence and interest in building with earth which is emerging in present-day architectural production (figs. 25, 26 and 27).

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1. Masonry principles A compressed earth block masonry structure consists of small building elements placed one on top of the other following a particular bonding pattern and bound together with mortar.

The earth blocks therefore form a building system - whether it be a wall or a partition, a post or a pillar, an arch, a vault or a dome - which has compressive strength. This characteristic of compressive strength is indeed essential as, by contrast, masonry structures using small elements have very little tensile strength.

The good strength and good stability of a masonry structure using small elements is dependent on the interaction of several factors:

- the quality of the block itself, - the quality of the masonry (i.e. the interaction between the block, the bonding pattern and

the mortar), - the form of the building system, which should be suited to the compressive forces exerted, - the quality of detailing of the building system, notably ensuring good protection against water

and humidity, - the quality of execution of the work.

Fig. 29: What is CEB masonry Fig. 30: What part does mortar play in CEB masonry

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Good compressive strength implies

The shape must suit the masonry structure

Fig. 31: The quality of CEB masonry

Possible uses of compressed earth block masonry

Compressed earth block masonry can be used for any kind of structure required by compressive forces:

Fig. 32: Wich building systems to use with CEBs?

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Mortar

FIGURE (FIG.33;34;35) Fig. 33: Laying the right amount of mortar. Fig. 34: Spreading the mortar out evenly. Fig. 35: Pre-soaking stabilized blocks.

Definition A mortar is a mixture of aggregates (sand and fine gravel) with a binding agent (generally cement or lime), to which water is added in previously determined proportions. Used in a plastic state, mortar ensures good mechanical bonding between the masonry elements making up a wall, a pillar, or other building systems.

Role In compressed earth block construction, as in construction using other masonry elements (such as stones, fired bricks, sand-cement blocks), mortar plays a threefold role:

- It bonds the masonry elements together in all directions (vertical and horizontal joints). - It allows forces to be transmitted between the elements and notably vertical forces (i.e. the

weight of the elements themselves, or applied forces). - It enables these forces to be distributed across the whole surface of the masonry elements. - It compensates for any defects in horizontality in the execution of the masonry work.

Properties and characteristics When freshly mixed, mortar should be easily "worked". Apart from having a suitable consistency, it should display good cohesion, as well as the capacity to retain water against the suction of the masonry elements on which it is applied.

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Apart from its consistency, mortar used for compressed earth block construction should:

- Be able to change shape. - Allow good permeability to humidity. - Have mechanical performances which are compatible with that of the compressed earth

blocks.

Composition The composition of the mortar should in each case take account of the actual requirements of the masonry structure. A good mortar should have good mechanical strength and should have the same compressive strength and resistance to erosion as the compressed earth blocks. Too low a strength mortar carries the risk of erosion, water infiltration and the deterioration of the compressed earth blocks. Erosion and cracking of the mortar, in addition to tensile forces, results in a risk of rupture. Too high a strength mortar carries the risk of water stagnating on parts of the visible mortar matrix standing proud of the surface which in turn causes the erosion of the blocks; this can result in the blocks cracking and in lowering their strength. The texture of a good mortar is generally more sandy than that of compressed earth blocks, with a maximum particle diameter of 2 to 5 mm. Stabilized mortar must always be used with stabilized compressed earth blocks. In this event, the proportion of cement or lime used should be increased by a factor of 1.5 or 2 to achieve the same strength as the earth blocks. It could be possible to use a non-stabilized earth mortar if one is sure that the walls which are to be built with this mortar are well sheltered from exposure to rain or to water in general. But even so, it will still be necessary to ensure that the non-stabilized mortar has the same compressive strength and resistance to erosion as the earth blocks.

FIGURE (FIG.36;37;38) Fig. 36: Spreading mortar well on the to be bounded. Fig. 37: Laying the block with a sliding motion. Fig. 38: Pushing the block firmly into place without hiting it.

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FIGURE (FIG.39;40;41) Fig. 39: Removing excess mortar. Fig. 40: Smooting the horizontal joints. Fig. 41: Smooting the vertical joints.

Disadvantages Mortars have certain weaknesses:

- they shrink as they dry out, - they can be chemically unstable, - they can present a lower strength surface at the point of contact between the mortar and the

block in a solid state. The main disadvantage is due to the hardening through drying out with a significant risk of shrinkage occurring. This shrinkage can cause the masonry to settle. This danger can be avoided by not making joints too wide, by using a fairly sandy mortar, or by wedging the joint apart by adding small stones.

Good practice The mixing water of the mortar should be clean (i.e. clear and non-acidic). The surface to which it is to be applied should be prepared and clean. The bonding of the blocks should be correct in both directions of the bonding pattern, using vertical and horizontal joints. Vertical joints should be well filled. Care should be taken to prevent the mortar drying out too quickly (e.g. sprinkling the wall in hot countries) and in general to avoid dramatic changes in temperature (special care must be taken in regions where the diurnal temperature range is particularly great.) The width of the mortar joints, both horizontal and vertical, should be even and a maximum of 1 to 1.5 cm. For stabilized compressed earth blocks, blocks should be pre-soaked, and the surface on which they are to be placed should also be moistened. The block should be "spread" with the right quantities of mortar on the sides to be bonded. Once the block has been laid, it should be pushed firmly into place, but above all it should never be tapped or hit as this could destroy the adherence between the block and the mortar.

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The joints should be smoothed as soon as the blocks have been laid, either using a jointer, or a piece of wet plastic tubing, wood or bamboo. Fig. 43: Finished appearance of joints. Joints can be finished in three ways, giving different appearances: 1 - flush with the wall 2 - slightly hollowed out (concave) and rounded 3 - hollowed out (concave) and chamfered

FIGURE (FIG.42;43) Fig. 42: Brushing for the final finish. Fig. 43: There are three possible types of joint.

Bonding patterns The term "bonding pattern" refers to the way in which compressed earth blocks are arranged, assembled and therefore bonded together in all directions of a masonry structure (horizontally and vertically, and in the thickness of the wall). The bonding pattern determines the position of each earth block from one course to another and notably prevents vertical joints occurring one immediately above the other, which would entail the risk of cracks spreading through the structure. Bonding patterns play an essential part in ensuring the cohesion, the stability and the strength of masonry structures built from small elements bonded together with mortar. Deciding which bonding pattern to use should be done before the masonry work begins will depend on five interrelated factors which should be considered together: 1 - the type of structure (wall, partition, pillar, other), 2 - the size of the structure, 3 - the dimensions of the compressed earth blocks, 4 - the skill of the masons (appropriate level of complexity), 5 - the aesthetic effect required of the finished appearance of the external faces of the structure.

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TERMINOLOGY FOR TYPES OF BONDING PATTERN (FIG.44)

Fig. 44: Basic terminology of ways of laying blocks to form bonding patterns using small masonry elements.

Fig. 45: Fundamental rules of bonding patterns to avoid superimposed vertical joints. (A;B;C;D) A;B) A good bonding pattern has no superimposed vertical joints, i.e. no vertical joint immediately above another between the bonding pattern therefore consists of courses laid alternately and shifted along, using one or two types of bonding pattern. C;D) Generally, the minimum distance between two blocks in two successive courses should be equal to a quarter of the logest side of the block (its length). To build simple earth block masonry structures, such as walls, the most common bonding patterns require the use of half and three-quarter dimension blocks, as well as of full blocks Fig. 46 shows a half block being used at the end of a wall, the width of which is equal to a half block. Fig. 47 shows a three-quarter block being used at the end of a wall, the width of which is equal to a full block.

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FIGURE (FIG.46;47) Fig. 46: "Half-block" thickness wall. Fig. 47: One-block thickness wall. TERMS OF BLOCK DIMENSIONS

THICKNESS OF THE MORTAR JOINT (jt) (FIG.48)

Fig. 48: Terms and rules for block dimensions using simple bonding patterns.

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DIMENSIONS OF COMMON BLOCK AND DERIVATES (FIG.49)

Fig. 49: The most common dimensions of compressed earth blocks and its derivates ( common half and three quarter blocks). A few examples of bonding patterns for walls the width of which is equal to a half-block. These bonding patterns use full' half and three-quarter blocks.

FIGURE(FIG.50;51;52) Fig. 50: half block used at the end of alternate courses and continuous wall. Fig. 51: Corner of wall using full block Fig. 52: "T"-shaped bonding pattern using three-quater blocks

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FIGURE(FIG.53) Fig. 53: "X"-shaped and "T"-shaped bonding patterns using three-quarter blocks. A few examples of bonding patterns for walls the width of which is equal to a full block. These bonding patterns use full, half and three-quarter blocks.

FIGURE(FIG.54;55) Fig. 54: Three-quarter block alternate courses and continuous wall. Fig. 55: "L" and "T"-shaped bonding patterns using three-quarter blocks

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FIGURE(FIG.56) Fig. 56: "X" -shaped and bonding patterns using full blocks and "T"-shaped bonding patterns using three-quarter blocks. Header bonding patterns for wall systems where the width of the wall is equal to a full block often require the use of a three-quarter block. Here it is shown being used at the end of a continuous wall and at the junction of two walls in an "L" or "T" shape.

FIGURE(FIG.57)

Fig. 57: A few examples of header bonding patterns for walls one block thick.

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More sophisticated header and stretcher bonding patterns, still for walls the width of which is equal to a full block, can combine the use of full blocks cut across their width, full blocks cut lengthways, and quarter blocks. These solutions should, however, be avoided as they can weaken the structure of the corner.

In this example (Fig. 58 a) of a corner using headers and stretchers, the two three-quarter blocks are replaced by a full block and a half-block cut lengthways.

FIGURE(FIG.58a) Fig. 58 a: Corner bonded using headers and stretchers without three-quarter blocks.

In this example (Fig 58 b) of a corner using headers and stretchers, a three-quarter block is combined with the remaining 1/4 block which would otherwise be wasted when the full block is cut.

FIGURE(FIG.58b) Fig. 58 b: Using a quarter of a block with a three quarter block.

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Bonding patterns for small section posts or pillars (30 x 30 cm or 30 x 45 cm) generally require full blocks and use a rotating pattern or reversed symmetrical patterns.

Fig. 59 a: Simple bonding pattern for a 30 cm pillar. Fig. 59 b: Simple bonding pattern for a 30x45 cm pillar. Bonding patterns for large section pillars (45 x 45 cm or 60 x 60 cm) use the three-quarter block in classic designs. Simplified patterns can require only the use of a full block.

Fig. 61 a: Classic bonding pattern for a 45 x 45 cm pillar. Fig 61 b: Simplified bonding pattern for a 45 x 45 cm pillar.

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Fig. 61 c: Classic bonding pattern for a 60 x 60 cm pillar.

Fig 61 b: Simplified bonding pattern for a 60 x 60 cm pillar.

Fig. 62: Squre block and half block obtained by cutting it down the middle. The square compressed earth block is derived from the traditional adobe brick of the same shape and which is used notably in Latin American building cultures which have their roots in pre-Columban history (Peru, Columbia, Equator, Bolivia). Recent presses allow moulds to be modified for square shapes. This shape is very useful for reinforced building systems and has been used in model earthquake resistant housing operations in Peru and in the Philippines, as it enables vertical reinforcement made of wood or steel to be easily inserted into the thickness of the walls.

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Fig. 63 a: Corner of wall. Fig. 63 b: Walls crosing in "X" con-figuration.

Coursing Building using small masonry elements has the advantage of great flexibility in use resulting from a complete mastery of the modular use of the material. This modulation combined with the dimensioning of building systems can be determined as a function of the size of the building element, i.e. of the compressed earth block. It can also be determined as a function of the principles of the block bonding patterns which are used in the development of building systems. "Coursing" is the link which the designer establishes between the dimensions of the compressed earth block, the dimensioning of the building systems, and their architectural representation in plan, elevation, section or detail. Coursing a compressed earth block architectural plan is indispensable when preparing working drawings. It ensures good project control in several ways: - Coursing enables one to establish exact dimensions for the working drawings, in plan and elevation, and thus to obtain precise quantitative data for the project. A well coursed set of working drawings will be put to good use at the later stage of producing the compressed earth blocks for the execution of the work on site, by specifying the exact number of blocks required. It will also enable

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losses resulting from too much waste during cutting to be monitored by specifying how many full, 3/4 and 1/4 blocks are required. - By enabling the implementation of the works and the quality of the building systems used to be controlled, coursing enables one to determine the exact dimensions of bays in the walls (door and wall openings), the position of a ring-beam, the location of floor beams in a wall etc. All this precision will be apparent in the quality of the finished structure. - It contributes to the appearance of the project, by highlighting the attractiveness of the material in the masonry of a visible compressed earth block wall. Precise modulation, thanks to coursing, underlies the aesthetic effect of all masonry using small elements which results from the appearance of rythmic sequences in the visible wall. COURSING, BONDING PATTERNS, MODULATION AND DIMENSIONING

Fig. 65: Rules for quantifying straight, "L" and "U" shaped walls.

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Fig. 66: Table of dimensions of straight, "L" and "U" shaped walls.

COURSING THE PLAN Coursing the geometrical representations of the working drawings for a compressed earth block masonry structure starts with the coursing of the plan. This is done with a carefully prepared working drawing. The scale of the working drawing should be such as to make it easy to read. For this reason 1/50 (2 cm/m) is often preferred over 1/100 (1 cm/m). Coursing the working plan must be done "globally" and not in a fragmented way, which could result in confusion when trying to bring together the different fragments of the quantified plan. Coursing the plan is done for each different course of earth blocks and generally for the "first" and "second" courses. But it is also often necessary to determine precise quantities for block courses located in a particular position in the future building, for example ring beam courses, when it has been decided to use lost formwork built from earth blocks. Another example would be a structure erected with thick ground floor walls, and less thick first floor walls. Note that the modulation of the

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openings is done using the nominal (or work) dimensions of the earth block used and that their dimensioning is done flush with the inside edges of the reveals for openings. Dimensions of the coursed plan result from the application of rules of modulation and of dimensioning (see figs. 65 and 66, p. 29). Coursing a plan assuming the use of a parallelepiped earth block measuring 29.5 x 14 x 9 cm, and 1.5 cm mortar joints. The wall thickness is equivalent to 1/2 a block.

FIGURE COURSING ELEVATIONS

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The vertical coursing of the facades, working up from the plan, is just as important and indispensable as coursing the plan. It provides the exact number of earth block courses and enables careful control of the vertical dimensions of the openings, the position of the ring-beam, the location of floor-beams in the walls, using the modulation of the height of the blocks and the thickness of the mortar joints. Certain building systems can be sufficiently complex to demand vertical coursing, in elevation or in section.

Fig. 68: Example of vertical coursing of a faade and of vertical sections of a wall with openings.

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2. The project's building dispositions

"Design skill" and "Building skill" are worth more than "Shielding skill" Good architectural design and good building work depend on the knowledge and skills of designers and builders. it is by renewing links with a long tradition of earth "design skill" and "building skill" and by making good use of recent technological inputs, that high quality earth architecture can be produced. There are a number of regional sayings which reflect this popular common sense and wisdom, such as this saying from Devon in England: "All cob wants is a good hat and a good pair of shoes", in other words a good roof and good footings. This "architectural skill" and this "building skill" are unfortunately often overshadowed by what we will call here "shielding skill", that is to say a current trend in building with earth which draws more on sometimes very sophisticated engineering with the aim of increasing the water resistance of "earth", whilst overlooking the tried and tested traditional approach, which consists in making the "building" water resistant, i.e. in fully integrating the central role of architectural design to ensure the quality, the performance, the strength and the durability of structures. This shielding approach is unfortunately very often used to provide an elaborate disguise to mask the defects of a poor architectural design or of a design which is not specific to earth as a building material and which borrows inappropriately from concrete or hollow cement block construction.

The main problems to resolve These fall into two categories: - On the one hand, structural problems which force one to respect the principles of good

compressive strength and, by contrast, the poor tensile and shearing strength of earth as a building material. In respecting these principles, the designer must choose between appropriate structural designs and construction details.

- On the other hand, problems of water and humidity, resulting from what is know as the "drop of

water system": erosion, streaming water, splash-back, infiltration, absorption. These problems make the designer respect certain fundamental principals: protecting the top and the base of the walls ("a good hat and good shoes"), allowing the earth building material to breathe and incorporating suitable details into the design principles.

EXAMPLES OF STRUCTURAL PROBLEMS (FIG.71;72;73)

Fig. 71: Absorbing the forces exerted vaults. Fig. 72: Spreading the load of the forces exerted by floors on the wall. Fig. 73: Absobing the arches.

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EXAMPLES OF HUMIDITY PROBLEMS (FIG.74;75;76)

Fig. 74: Problems of humidity at the base of wals. Fig. 75: Problems of humidity at the level of the openings. Fig. 76: Allowing the wall to breate

Types of wall Compressed earth block masonry enables one to build either loadbearing walls, both thick and thin, or non-loadbearing walls such as partitions which divide up the space within a building. This simple classification offers great architectural flexibility.

Main problems For masonry wall systems as a whole, the main problems result from the nature of the stresses which are applied to them. - Crushing: under the effect of the weight of the wall itself or of a concentrated vertical load. - Vertical excentric loads resulting from a tensile force (bending out at floor level, for example). - Horizontal excentric loads resulting from the pressure of a vault on the walls for example. - Buckling resulting from the accumulated effect of a load stress and from the settling of a wall

which is too thin and too high by comparison for example. - Horizontal loads. These fall into two kinds. On the one hand the uniform pressure of winds on

the walls, and on the other the concentrated pressure of earthquakes (i.e. high tensile and bending stress).

Solutions For non-loadbearing walls, infill masonry (of a concrete framework of wooden lattice) limits the risk of crushing occuring. For loadbearing walls, there are several solutions which enable the forces of excentric loads, of buckling or of horizontal loads to be reduced. These include: - using the thickness of the walls; - improving the stability of thin walls by using buttresses; - improving the stability of thin walls by using ring-beams; - adding horizontal and vertical reinforcement to the masonry, (earthquake-resistant systems).

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FIGURE (FIG.77;78) Fig. 77: Five great problem. Fig. 78: Five good solutions.

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Types of structure

Five essential rules of good practice Building in compressed earth blocks, over and above the specific factors common to all techniques of masonry using small elements, sends the designer and builder directly back to the rules of "good practice" for designing and building with earth. These essential rules of good practice can be summarized under five headings: - Knowing the material, its physical characteristics, properties and mechanical performances. - Knowing the particularities of the earth building technique employed, the special equipment it

requires and the specific ways in which it is applied. - Adopting simple building systems which are compatible with the way of using the material: good

compressive strength, poor tensile, bending and shearing strengths. - Adopting design principles and building solutions which are proper to building with earth, taking

care to protect the parts of the building which are exposed to the main causes of degradation (water for example).

- Ensuring that the execution of the building work is carefully carried out.

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Fig. 79: Table showing the links between structural principles, types of wall and openings and the architectural resources of the plan.

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Foundations and footings

Two types of problem Particular care should be taken with the foundations and footings of a compressed earth block building and the building should be protected from two main types of problem: - structural problems, - problems linked to humidity. This is because buildings constructed from compressed earth blocks, by the very nature of the material, are vulnerable to inherent structural risks or to humidity which can cause very serious damage. One must therefore be particularly vigilant in respecting the rules and codes of good practice which are specific to building with earth. This does not mean, however, that problems stem only from the nature of the material; they can arise because of external factors - differential settling, landslides, and natural disasters such as earthquakes and floods - which will be even more damaging if the building has been badly designed or built.

Choosing a system of foundations and footings This will depend on the nature of the ground on which the structure is to be built and the type of structure envisaged. There is a danger of structural weakness when building on unstable or weak sites. This danger can be increased by a poor design (underdimensionning or insufficient strength for example) or if the foundations are badly built (located excentrically to the downward loads for example). On poorly-drained sites, humidity can increase the risk of structural weakness as this can considerably weaken the cohesion of the material, its strength and therefore that of the wall. The problems outlined here should not, however, lead one to overdimension the foundations and footings, nor to make too great a use of reinforced concrete. The choice of foundations and footings should above all be well-suited to the nature of the ground, the nature of the building (private or open to the public), the nature of the loads and permissible overloads, the climatic constraints of the environment (rain, snow, wind, etc.), the building principles of the structure (the type and thickness of wall, whether or not there is a cellar or a sanitary pit, etc.). The table in fig. 81 suggests structural designs for foundations and footings given the nature of the wall systems and the site ground.

Fig. 80: Key to figure 81.

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Fig. 81: Summary table of structural concepts depending on the type of wall and the nature of the ground for the foundation.

Water and humidity: a danger not to be underestimated Earth buildings, whether built from compressed Barth blocks or from other earth building materials, remain particularly vulnerable to water. The designer of earth buildings must be well aware of this danger and must not underestimate its importance. He should take appropriate measures to eliminate it. It is vital to remove sources of humidity, particularly at the base of walls and at the level of foundations and footings.

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Fig. 82: Weakness due to prolonged exposure to humidity

Problems with foundations At the base of the walls, from the foundations upwards, the danger of capillary rise can stem from several sources: seasonal fluctuations in the water table, water retention by plants or shrubs growing too close to the walls, damage to the clean water supply or waste water system, absence of drainage, a damaged drainage system, or stagnation of water at the base of the walls. A lengthy period of humidity can weaken the base of earth walls, notably when the material loses its cohesion and passes from a solid to a plastic state. The base of the wall may then no longer be able to support the loads and will be in danger of collapsing. Humidity also encourages the emergence of saline efflorescences which attack the materials and hollow out cavities where small animals can nest (insects, rodents, etc.) and this can further aggravate the process of wearing away which has already started.

Fig. 83: Weakness due to humidity undermining the base

Problems with footings Above the natural ground level, the base of the wall can be attacked by water. This can be due to water splashing back, waterspouts, badly designed or damaged gutters, puddles being splashed by passing vehicles, washing the floors inside, morning condensation (or dew), a roadway gutter flowing too close to the wall, surface waterproofing (cement pavement) which prevents evaporation from the soil, a water-proofing render which causes moisture to be trapped between the wall and the render or the growth of parasitical flora (such as moss) and saline efflorescences.

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All these problems are well-known and completely solvable. The informed designer should not on the other hand adopt a "shielding" approach, which might not only be very expensive but could also provoke the very weaknesses it seeks to avoid by excessive water-proofing. Above all the building must be allowed to breathe. The correct attitude is to resolve the problems by attacking their causes, not their effects. Appropriate solutions can only emerge from a good understanding of the nature of the various risks which we detail below.

Fig. 84: Weakness due to humidity resulting from excesive waterproofing.

Fig. 85: Key to figs. 82 to 93. HUMIDITY RISKS

Infiltration without accumulation This humidity risk is very common where the foundations are built on a permeable site, the geotechnical composition of which is predominantly sand and/or gravel. This type of site ensures good drainage away from the building. When it rains, water infiltrates rapidly from the surface to underground. This infiltrated water does not therefore get the chance to accumulate and stay in contact with the foundations. There is therefore no risk of sufficient capillary rise to reach the wall and cause damage.

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Fig. 86: Infiltration without accumulation.

Infiltration with temporary accumulation This risk frequently occurs in cohesive clay or silty soils. If the way the foundation is built is combined with good surface drainage, such as the one shown in diagrammatic form in fig. 87, in the form of an incline draining water away from the building, then this humidity risk is less great. In a cohesive soil, water penetrates less quickly from the surface to underground and towards the infill material. The latter, when it consists of permeable material (sand and gravel, for example) will only accumulate water temporarily, but this water will have difficulty in disappearing from the adjacent cohesive soil. Nevertheless, this kind of temporary accumulation can result in water suction occuring in the foundations for a short time.

Fig. 87: Temopary accumulation.

Infiltration with prolonged accumulation This risk can occur in all types of soil with poor surface drainage, even permeable, sandy and or gravelly soils when the ground slopes towards the building (a situation to be avoided at all costs). In this event, the slope acts as a captor and accumulator of water, which then stays in prolonged contact with the foundations. Capillary rise follows, and this can be significant during the rainy season. This capillary rise, depending on the design of the building, can even reach the footings and the base of the wall. Serious damage can occur.

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Fig. 88: Prolonged accumulation.

Capillary rise with or without infiltration The most serious humidity risk occurs when the structure is in contact with or in close proximity to the water table. When the foundations are directly in contact with this water table, capillary action is continuous. This phenomenon is all the more sensitive when the soil is cohesive as the latter, once saturated with water, remains in a permanents/ate of humidity. In a permeable soil when the foundations are always above the level of the ground water, a normal cycle of evaporation can take place and the danger is less, but still present. The permanent exposure of the foundations to the risk of capillary rise represents a great danger of damage to the base of the structure.

Fig. 89: Capillary rise.

Infiltration without accumulation Since the water disappears very quickly underground, all that needs to be done is to evacuate as quickly as possible the same amount of remaining water which penetrates towards the foundations. In this case, the foundations and footings can be subjected to the weak capillary risk resulting from the infiltration, but they must without fail be able to withstand the risks of water flow and/or water splash-back occurring at the base of the structure, at the surface. The use of materials such as stone, fired brick or rendered sand-cement block can reduce this risk. Any rendering can be restricted to the interior surface of the footing in order to leave the way open for evaporation towards the outside to occur and to avoid any humidity traces on the inside. It is not necessary to use impermeable materials for the foundations nor to install a drainage system.

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Fig. 90: Several examples of how to treat a humidity risk resulting from infiltration without accumulation.

Infiltration with temporary accumulation Since in this case the cohesive soil absorbs water, good surface drainage is required in order to evacuate water from the vicinity of the building. A pavement or banking up may suffice but care must be taken not to make these impermeable to migrations of humidity or moisture. This is unfortunately what often occurs when, with the best of intentions, a pavement made of too high dosage cement is built. This prevents even the small amount of water which remains at the level of the foundations from escaping, since it is trapped by the impermeable surface and so naturally moves towards the footings and the base of the wall. There is no need to use an impermeable render, or even a bitumen one, on the vertical face of the foundations, nor to build impermeable foundations, nor even a deep drainage system, since the water accumulation is only temporary. The structure must be allowed to breathe.

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Fig. 91: Several examples of how to treat a humidity risk resulting from infiltration with temporary accumulation. EXAMPLES OF SOLUTIONS

Infiltration with prolonged accumulation When there is a danger of prolonged water infiltration, the water must be intercepted before it penetrates underground and evacuated as quickly as possible. The principle of drainage is perfectly appropriate here. Drains can be built right against the foundations but then the external vertical surface of the foundations will have to be rendered or made impermeable. They can also be installed at